Process of manufacturing photographic elements



Patented Dec. 19, 1950 PRooEss OF MANUFACTURING PHOTO= GRAPHIC ELEMENTS Clay Weaver, Wilmington DeL, assignorto E. I. duPontde Nemours'& Company, Wilmington, "DeL, a'corporation of Delaware .NoDrawing. Application November 27,1946, SerialNo. 712,721

-Claims. 1

This invention relates to photographic elements bearing gelled layers of synthetic hydroxyl I polymer-silver halide emulsionsand to processes of preparing the same.

The coating of synthetic hydroxyl polymersilver halidev emulsions in thin, uniform layers is quite diflicult to carry out on a continuous commercial scale. Such emulsions do not gel or set like gelatinwith slight variations in temperature. when heatis used to drive fi'thesolv ent, the layers can be coated'fairly rapidly but are not uniform in thickness. It has been proposed to add various types of gelling agents to polyvinyl alcohol compositions to :improve their coating properties. They, are. generally. added during the preparation of the emulsion. This practice, while useful for small-scaleoperations, hassomecdisadvantagesforlargeescalecommercial-operations. The emulsionssoften gel or set up in theCQntainers, or; coating, apparatus and'continued contact, with the a ents causes a ch n e. np ot e grephiccpropertiesi T e. lay r l k u f rm y because the s llin a n cont n e. ac pon storage,

An object of this invention is to provide improvements in the artof coating synthetic hydroxyl polymer layers and especially silver halide emulsions. A further object is to provide a simple process for controlling. the gelling of silver halide hydroxyl polymeremulsion layers.

A still iurtherobjectis' to provide sucha process, which canbe used on v a continuous commercial scale. Still other objects willfbe apparent from the following descriptionoi' the invention.

It hasbeen discovered, andthis is the basis of the present invention, that gelled synthetic hydroxyl polymer layers and especially silver halide synthetic ,hydroxyl polymer silver salt emulsion layers having good, surface. characteristics and quality can be made. by coating fluid mixtures of such polymers and silverhalide ,ernulsions having a WpH greater than 7.0 onto a layer comprising substantial amounts of a soluble boron com o nd wh o m bq t onin aqueous solution. e. g., boric acid and its esters and salts. The boron compounds are preferably incorporated in a ,hydrophilic colloid layer which has good adherence tov synthetic hydroxyl polymers. It is preferably composed of a synthetic hydroxyl polymer. The hydrophilic colloid layer contai t e bo n c m undm y be depos ed directly on ,the support or on an anchoring $llbstratum.

A silver halide emulsion or dispersion in various ty of w t r-soluble o d on lic synt etic rqx l o yme v or xamp cen e di e led b cq tins uc an. em ls o Onto. a are c n ainin sh w q lpq nd as Specified. abdii- Th H o h co t d. m l' i layer "Should be greater than '7. This can be aCcOmpIiShd bl! adjusting l'the pI-I of the sublayer ande before coating Thesoluble'looron fc'ompoun apparently diffusesi'into" the "silver halide em" sion layer and-under the alkali conditionstliere encountered causesithe silver, h emulsionto gel orset' atf'a rapid rate. Q'Ih gelling takes effect progressively from" the "bet 7 'n iupwards'. After drying has bee'nfcornpleted iti isilsin hard, uniform; and of excellentqualit'y. Em sion coatings of the usual thickness arelgellfedpr set in accordancewith this invention in a matter of a few seconds. t

By synthetic hydroxyl; polymer isineanta linear polymer containing a plurality oir'e' curr' -ing intralinear vinyl alcohol (,C H2--CHOH'' groups.

Synthetic hydroxyl poly me rs.of the water? soluble tov hydrophilic type including polyvinyl alcohol and itsv partially hydrolyzed waterfsolub e lower fatty acid esters, loweralkyl sphere; lower acetals have been proposed as silver de binding agents for photographic elements. vinyl alcohol is a tough, water-white, polyp; film forming" material. It is-soluble in "waterl The more highly polymerized varieties are soluble in hot water. and; the medium or lower polymers are. soluble in cold water. 'They are usua pared byhydrolysis of polyvinyl estersj'su polyvinyl acetate, polyvinyl chlora'eetate, pol vinyl isobutyrate, etc. The -partly'-hydr esters which contain a large number of vinyl alcohol units (--CH2-'CHOH) are soluble in character. The ethers can'be by incompletely etherifying the completely or partially hydrolyzedpolyvinyl acetate, etc. The polyvinyl acetals, e. g., polyvinyl acetaldehyde acetal' and-polyvinyl isobutyral; can be made byacetalization of polyvinyl alcohol andits'inconi pletely hydrolyzed carboxylic acid esters.

In-addition; to thewater-solubleand hydro; philic synthetic hydroxyl polymers justdeseribe there maybe mentionedpartially andcomp te hydrolyzed polyvinyl-esters, e. g, and copolyiners thereof withethylemoa saturated compounds,- -such as vinyl chlorideand. f styrene; acrylic acid esters, e. .',metny1 ary1 e; z, methacrylic ,acid esters, e. g., methyl methacrylatej and mono-olefines e.'g., ethylene. The completely hydrolyzed ethylene/vinyl acetate copolymer emulsion described in McQueen 2',39'7,86:6 and Roland 2,386,3{1 form an important class ade of silver halide emulsions which can advantageously be coated by the improved methods in question. These polymers may contain colorformer nuclei. Suitable polymers of this latter type are described in United States Patents 2,310,943 and 2,320,422 and in United States applications Serial Numbers 528,946 now Patent Number 2,415,381 and 528,943 now Patent Number 2,397,865.

When a synthetic hydroxy1 polymer is used as the colloid for the sublayer it is necessary to adjust the pH of the coating solution to 7.0 or lower so that uniform sublayers can be formed. This may be accomplished by the addition of small amounts of a readily soluble acid, e. g., glycolic acid, acetic acid, diglycolic acid, etc., or acid reacting salts, e. g., ammonium nitrate and ammonium chloride.

The soluble boron compounds are used in amounts sufficient to give complete gelling of the over-coated synthetic hydroxyl polymersilver halide emulsion layer. The amounts, of course, vary in accordance with the particular hydroxyl polymer emulsion to be gelled. In general, amounts from 20 to 60% by weight of the polymer to be coated onto the sublayer are sufficient to gel the silver halide emulsion coatings.

The soluble boron compounds may be deposited directly on the support, e. g., paper, metal, synthetic resin, or super polymer, cellulose derivative, glass, etc., from an aqueous solution or dispersion or from a solvent or onto a sublayer which has good anchorage characteristics.

The invention will be further illustrated but is not intended to be limited by the following examples. The parts are by weight.

Example I A hydrolyzed ethylene/vinyl acetate interpolymer of the type described in Example I of United States Patent 2,397,866 in an amount of one part was dissolved in a mixture of 40 parts of ethanol and 60 parts of water. One tenth part of boric acid and one-tenth part of diethylene glycol were added and the resulting mixture coated onto a cellulose acetate film base and the resulting layer was dried. A lightsensitive emulsion containing silver halide grains dispersed in the same type of hydrophilic interpolymer and having a pH of 8 to 9 was coated onto the sublayer. The emulsion gelled rapidly when applied and a smooth coating was obtained.

Similar results can be obtained by substituting for the boric acid equivalent amounts of boric acid esters, e. g., diethylene glycol boriborate, mannitol borate, etc.

Example II ,A double weight raw paper is coated with a solution made by adding 7.58 grams of ammonium sulfate in 70.5 cc. of water to 470 grams of a 10% solution of the interpolymer set forth in Example I. To the mixture is added in thirty seconds 11.75 grams of barium chloride in 470 cc. of water, 3 cc. of an 0.5% solution of Monastral Blue BWD, 5 cc. of a 5% saponin solution, 200 cc. of a, aqueous solution of diethylene glycol boriborate, and 5.7 grams of glycolic acid. The coating is dried for 30 minutes at 40 C. One hundred cubic centimeters (100 cc.) of the silver halide emulsion described in Example I but containing 3 cc. of 6N KOH is coated onto the sublayer. Firm gelation of the emulsion layer occurs in 30 seconds.

The diethylene glycol boriborate of this ex- 4 ample can be made by reacting diethylene glycol, boric acid, and borax at 100 to 160 C. as described in United States Patent 1,953,741. It can also be replaced by an equivalent amount of boric acid and diethylene glycol.

Example III Ten parts of an acetal of a hydrolyzed ethylene/vinyl acetate copolymer (ethylene/vinyl acetate ratio l/ 10) with benzaldehyde-ortho-sulfonic acid prepared as described in Example I of application Serial Number 551,801, filed August 30, 1944, now abandoned, and the continuation-in-part thereof Serial Number 698,799, filed September 23, 1946, now Patent Number 2,462,151 is dissolved in a mixture of 25 parts of water and 175 parts of methanol. To this is added a solution of three parts of boric acid and three parts of diethylene glycol in a mixture of 25 parts of water and parts of methanol. This solution is then diluted to 1000 parts with a 50/50 mixture of methanol and ethanol. Cellulose nitrate film base is coated with this solution and after drying it is coated with a silver halide emulsion in hydrolyzed ethylene/vinyl acetate prepared as described in Example I of United States Patent 2,397,866 and having a pH of 7.5. Within 30 seconds after coating this emulsion layer sets to a firm gel which can be dried rapidly to a smooth, uniform, light-sensitive layer.

Example IV Ten parts of the mixed polyvinyl acetal of salicylaldehyde and phthalaldehydic acid, prepared as described in Example III of United States Patent 2,310,943, is used in place of the acetal of Example III hereof to form a substratum layer. Over this is coated a silver halide emulsion prepared in the polyvinyl acetal of salicylaldehyde as described in United States Patent 2,397,864, Example IV. The resulting light-sensitive coating is smooth and uniform and exhibits good anchorage, dry and wet.

Example V A subbed film base, prepared as in Example III, is coated with a 4% solution of hydrolyzed ethylene/vinyl acetate (see Example I of United States Patent 2,397,866) in ethanol/water (20/80) containing 4% by wei ht of comminuted silver. This non-halation layer dries to a smooth, uniform, light-absorbing film. In place of the comminuted silver, non-halation dyes may be used. Suitable dyes are described in United States Patent 2,203,767.

In place of the specific gelling agents described above, there may be substituted other boric acid esters or salts capable of yielding borate ions in aqueous solution. Suitable additional compounds include sodium and potassium tetraborate, metaborate, and orthoborate, boric acid, glyceryl borate, glycerol boriborate; the sorbitol, mannitol, and dulcitol monoborate and diborates and monoand poly-condensation products and their sodium and ammonium salts set forth in Examples 1 to 19 of United States Patent 2,223,349 and Examples 3, 4, 5, 7, 9, 14, and 18 to 35 of United States Patent 2,223,948. Moreover, suitable boric acid esters can be prepared by reacting a polyhydric alcohol, e.g., ethylene glycol, diethylene glycol, triethylene glycol, erythrol, sorbitol, and mannitol with boric acid or a mixture of boric acid and borax, by heating the admixture to to C. A copious ssesses evolution of water occurs. The resulting products are viscous syrup or resins of a colloidal nature and have a high molecular weight and complex structure. The are readily soluble in water but are substantially insoluble in hydrocarbons. Their preparation-isdescribedin v ,i- 0118 United States a ts nclud g :1, 5; ,-.7 1=i-: 2,223,349, 2,223,948, 2,223,949, and 2,224,011. These compounds have been referred to as boriborates.

The invention is not limited to the use of the gelling agents in a colloid substratum layer. Aqueous solutions of the gelling agents may be deposited directly on a support and the layer or coating to be gelled deposited thereon. In the case of hydrophobic supports, the anchorage is not sufiicient for permanency. However, good strippable gelled emulsion layers can be made by the latter technique. The gelling sublayers can be used to gel other types ofovercoatings than the silver halide emulsion layers described above. Thus clear colloid layers, filter layers, and anti-halation layers utilizing synthetic hydroxyl polymer binding agents can be coated in like manner. the sublayer containing the boron compound may also contain a pigment, e.g., baryta. In such cases alkaline agents may be added to the coating solutions to adjust the pH to more than 7.

Various water-miscible materials, such as solvents and/or crystallization inhibitors, may be added to the coating solutions for the gelling sublayers. Suitable such materials include ethanol, methanol, isopropanol, tertiary butanol,

dioxane, ethylene glycol, diethylene glycol, mannitol, the monomethyl ether of ethylene glycol, dimethylformamide, formamide, acetone, and dioxolane.

Various types of hydrophilic colloids may be used as binding media for the gelling agents including not only the synthetic hydrophilic hydroxyl polymers and colloids above-described but also galatin, casein, methyl cellulose, and the hydrophilic polyvinyl acetals containing solubilizin groups described in Woodward application Serial Number 551,801, filed August 30, 1944, now abandoned, and the continuation-inpart thereof Serial Number 698,799, filed September 23, 1946 now Patent Number 2,462,151.

The invention is useful in the preparation of photographic elements for various purposes. Thus it is useful in the preparation of photographic elements, such as motion picture and portrait films, lithographic film, printing plates, photographic papers, etc.

The invention is especially advantageous with supports which are diflicult to coat. It can be used on cellulose nitrate, cellulose acetate, cellulose propionate, cellulose acetate-propionate, cellulose acetate butyrate, polyvinyl chloride, glass, metal, regenerated cellulose, super polyamides (nylon), polyvinyl fluorides, etc.

An advantage of the invention is that it provides a simple method for gelling synthetic hydroxyl polymer silver halide emulsion layers. A further advantage is that the gelling of such layers can be efficiently controlled. A still further advantage is that it simplifies coating operations in that the emulsions do not substantially vary in viscosity during coatin operations. Since the gelling agents are not added to the coating solutions of the silver halide emulsions, there is no danger of having them set up or gel prior to coating. A further advantage resides in the fact that no color is imparted from In the case of photographic papers, A

6 the novel gelling agents. The gelling 'takes' efiect from the bottom of the coated layer up wardly givinga uni-form product. The action is very rapid and gelling takes place as the coating solution is applied to the layer containing the gelling agent. Another advantage is the avoidance of undesirable photographic changes in the applied emulsion.

As many apparently widely different embodiments of this invention maybe made without depar-tingi-rom'the spirit and scope thereof, it is to be understood that the invention is not *to be limited except as defined by the appended claims.

What is claimed is:

1. A process of manufacturing photographic elements which comprises coating a support with a solution of a synthetic hydroxyl polymer containing a substantial amount of a soluble boron compound capable of yielding borate ions, said solution having a pH less than 7.0, drying the layer and coating the resulting layer with a fluid silver halide emulsion in a synthetic hydroxyl polymer having a pH greater than 7.0, each said hydroxyl polymer being water-soluble to hydrophilic in character and containing a large number of recurring intralinear -CH2-(3HOH groups.

2. A process of manufacturing photographic elements which comprises coating a support with a solution of a synthetic hydroxyl polymer containing a substantial amount of boric acid, said solution having a pH less than 7.0, drying the lay er and coating the resulting layer with a fluid silver halide emulsion in a synthetic hydroxyl polymer having a pH greater than 7.0, each said hydroxyl polymer being water-soluble to hydrophilic in character and containing a large number of recurring intralinear groups.

3. A process of manufacturing photographic film elements which comprises coating a film base with a solution of a synthetic hydroxyl polymer containing a substantial amount of a soluble boron compound capable of yielding borate ions, said solution having a pH less than 7.0, drying the layer and coating the resulting layer with a fluid silver halide emulsion in a synthetic hydroxyl polymer having a pH greater than 7.0, each said hydroxyl polymer being water-soluble to hydrophilic in character and containing a large number of recurring intralinear 4. A process of manufacturing photographic film elements which comprises coating a film base with a solution of polyvinyl alcohol containing a substantial amount of a soluble boron compound capable of yielding borate ions, said solution having a pH less than 7.0, drying the layer and coating the resulting layer with a fluid silver halide emulsion in polyvinyl alcohol having a pH greater than 7.0.

5. A process of manufacturing photographic elements which comprises coating a paper support with a solution of a hydrophilic hydrolyzed ethylene/vinyl acetate copolymer containing finely divided baryta and a soluble boron compound capable of yielding borate ions, said solution having a pH less than 7.0, drying the layer and coating the resulting layer with a fluid silver halide emulsion in ,a hydrophilic hydrolyzed UNITED STATES PATENTS ethylene/vinyl acetate copolymer having a pH Number Name Date I greater than 7.0 each of said copolymers c n- 2249 538 McDowell July 15 1941 taining 21 l rge number of recurrin intralinear 212511296 Shim) 5' 1941 5 2,376,371 Lowe et a1 May 22, 1945 groups, "CHPCHOH 2,386,347 Roland Oct, 9,1945

CLAY WEAVER; 2 39 McQueen Apr. 2, 1946 REFERENCES CITED 1o 

1. A PROCESS OF MANUFACTURING PHOTOGRAPHIC ELEMENTS WHICH COMPRISES COATING A SUPPORT WITH A SOLUTION OF SYNTHETIC HYDROXYL POLYMER CONTAINING A SUBSTANTIAL AMOUNT OF A SOLUBLE BORON COMPOUND CAPABLE OF YIELDING BORATE IONS, SAID SOLUTION HAVING A PH LESS THAN 7.0, DRYING THE LAYER AND COATING THE RESULTING LAYER WITH A FLUID SILVER HALIDE EMULSION IN A SYNTHETIC HYDROXYL POLYMER HAVING A PH GREATER THAN 7.0 EACH SAID HYDROXYL POLYMER BEING WATER-SOLUBLE TO HYDROPHILLIC IN CHARACTER AND CONTAINING A LARGE NUMBER OF RECURRING INTRALINEAR 